Biostat 203B Homework 3

Due Feb 23 @ 11:59PM

Display machine information for reproducibility:

sessionInfo()

R version 4.3.1 (2023-06-16)
Platform: aarch64-apple-darwin20 (64-bit)
Running under: macOS Ventura 13.6.3

Matrix products: default
BLAS:   /Library/Frameworks/R.framework/Versions/4.3-arm64/Resources/lib/libRblas.0.dylib 
LAPACK: /Library/Frameworks/R.framework/Versions/4.3-arm64/Resources/lib/libRlapack.dylib;  LAPACK version 3.11.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

time zone: America/Los_Angeles
tzcode source: internal

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

loaded via a namespace (and not attached):
 [1] htmlwidgets_1.6.4 compiler_4.3.1    fastmap_1.1.1     cli_3.6.2        
 [5] tools_4.3.1       htmltools_0.5.7   yaml_2.3.8        rmarkdown_2.25   
 [9] knitr_1.45        jsonlite_1.8.8    xfun_0.41         digest_0.6.34    
[13] rlang_1.1.3       evaluate_0.23    

Load necessary libraries (you can add more as needed).

library(arrow)

Attaching package: 'arrow'

The following object is masked from 'package:utils':

    timestamp

library(memuse)
library(pryr)
library(R.utils)

Loading required package: R.oo

Loading required package: R.methodsS3

R.methodsS3 v1.8.2 (2022-06-13 22:00:14 UTC) successfully loaded. See ?R.methodsS3 for help.

R.oo v1.25.0 (2022-06-12 02:20:02 UTC) successfully loaded. See ?R.oo for help.

Attaching package: 'R.oo'

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    getClasses, getMethods

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    attach, detach, load, save

R.utils v2.12.3 (2023-11-18 01:00:02 UTC) successfully loaded. See ?R.utils for help.

Attaching package: 'R.utils'

The following object is masked from 'package:arrow':

    timestamp

The following object is masked from 'package:utils':

    timestamp

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    cat, commandArgs, getOption, isOpen, nullfile, parse, warnings

library(tidyverse)

── Attaching core tidyverse packages ──────────────────────── tidyverse 2.0.0 ──
✔ dplyr     1.1.4     ✔ readr     2.1.5
✔ forcats   1.0.0     ✔ stringr   1.5.1
✔ ggplot2   3.4.4     ✔ tibble    3.2.1
✔ lubridate 1.9.3     ✔ tidyr     1.3.0
✔ purrr     1.0.2     

── Conflicts ────────────────────────────────────────── tidyverse_conflicts() ──
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ℹ Use the conflicted package (<http://conflicted.r-lib.org/>) to force all conflicts to become errors

Display your machine memory.

memuse::Sys.meminfo()

Totalram:  16.000 GiB 
Freeram:    3.192 GiB 

In this exercise, we use tidyverse (ggplot2, dplyr, etc) to explore the MIMIC-IV data introduced in homework 1 and to build a cohort of ICU stays.

Q1. Visualizing patient trajectory

Visualizing a patient’s encounters in a health care system is a common task in clinical data analysis. In this question, we will visualize a patient’s ADT (admission-discharge-transfer) history and ICU vitals in the MIMIC-IV data.

Q1.1 ADT history

A patient’s ADT history records the time of admission, discharge, and transfer in the hospital. This figure shows the ADT history of the patient with subject_id 10001217 in the MIMIC-IV data. The x-axis is the calendar time, and the y-axis is the type of event (ADT, lab, procedure). The color of the line segment represents the care unit. The size of the line segment represents whether the care unit is an ICU/CCU. The crosses represent lab events, and the shape of the dots represents the type of procedure. The title of the figure shows the patient’s demographic information and the subtitle shows top 3 diagnoses.

Do a similar visualization for the patient with subject_id 10013310 using ggplot.

Hint: We need to pull information from data files patients.csv.gz, admissions.csv.gz, transfers.csv.gz, labevents.csv.gz, procedures_icd.csv.gz, diagnoses_icd.csv.gz, d_icd_procedures.csv.gz, and d_icd_diagnoses.csv.gz. For the big file labevents.csv.gz, use the Parquet format you generated in Homework 2. For reproducibility, make the Parquet folder labevents_pq available at the current working directory hw3, for example, by a symbolic link. Make your code reproducible.

Answer:

#read in data files
patients_tble <- read_csv("~/mimic/hosp/patients.csv.gz")
admissions_tble <- read_csv("~/mimic/hosp/admissions.csv.gz")
transfers_tble <- read_csv("~/mimic/hosp/transfers.csv.gz")
labevents_tble <- arrow::open_dataset("labevents_pq/part-0.parquet", 
                                      format = "parquet") |> as_tibble()
procedures_icd_tble <- read_csv("~/mimic/hosp/procedures_icd.csv.gz")
diagnoses_icd_tble <- read_csv("~/mimic/hosp/diagnoses_icd.csv.gz")
d_icd_procedures_tble <- read_csv("~/mimic/hosp/d_icd_procedures.csv.gz")
d_icd_diagnoses_tble <- read_csv("~/mimic/hosp/d_icd_diagnoses.csv.gz")

#define variables used in ggplot 
sid <- 10013310
#gender <- "F"
#patient_demo <- paste("Patient", sid, )

ggplot() +
  geom_segment(data = subset(transfers_tble, subject_id == sid),
               aes(x = intime, xend = outtime, y = 0, yend = 0, 
                   color = careunit)) +
  labs(title = "Patient 10013310, F, 70 years old, Black/African",
       x = "Calendar Time") +
  theme_bw() + 
  theme(legend.position = "bottom")

Q1.2 ICU stays

ICU stays are a subset of ADT history. This figure shows the vitals of the patient 10001217 during ICU stays. The x-axis is the calendar time, and the y-axis is the value of the vital. The color of the line represents the type of vital. The facet grid shows the abbreviation of the vital and the stay ID.

Do a similar visualization for the patient 10013310.

Answer:

ggplot(data = icustays_tble) +
  geom_line(aes(x = ))

Q2. ICU stays

icustays.csv.gz (https://mimic.mit.edu/docs/iv/modules/icu/icustays/) contains data about Intensive Care Units (ICU) stays. The first 10 lines are

zcat < ~/mimic/icu/icustays.csv.gz | head

subject_id,hadm_id,stay_id,first_careunit,last_careunit,intime,outtime,los
10000032,29079034,39553978,Medical Intensive Care Unit (MICU),Medical Intensive Care Unit (MICU),2180-07-23 14:00:00,2180-07-23 23:50:47,0.4102662037037037
10000980,26913865,39765666,Medical Intensive Care Unit (MICU),Medical Intensive Care Unit (MICU),2189-06-27 08:42:00,2189-06-27 20:38:27,0.4975347222222222
10001217,24597018,37067082,Surgical Intensive Care Unit (SICU),Surgical Intensive Care Unit (SICU),2157-11-20 19:18:02,2157-11-21 22:08:00,1.1180324074074075
10001217,27703517,34592300,Surgical Intensive Care Unit (SICU),Surgical Intensive Care Unit (SICU),2157-12-19 15:42:24,2157-12-20 14:27:41,0.9481134259259258
10001725,25563031,31205490,Medical/Surgical Intensive Care Unit (MICU/SICU),Medical/Surgical Intensive Care Unit (MICU/SICU),2110-04-11 15:52:22,2110-04-12 23:59:56,1.338587962962963
10001884,26184834,37510196,Medical Intensive Care Unit (MICU),Medical Intensive Care Unit (MICU),2131-01-11 04:20:05,2131-01-20 08:27:30,9.171817129629629
10002013,23581541,39060235,Cardiac Vascular Intensive Care Unit (CVICU),Cardiac Vascular Intensive Care Unit (CVICU),2160-05-18 10:00:53,2160-05-19 17:33:33,1.3143518518518518
10002155,20345487,32358465,Medical Intensive Care Unit (MICU),Medical Intensive Care Unit (MICU),2131-03-09 21:33:00,2131-03-10 18:09:21,0.8585763888888889
10002155,23822395,33685454,Coronary Care Unit (CCU),Coronary Care Unit (CCU),2129-08-04 12:45:00,2129-08-10 17:02:38,6.178912037037037

Q2.1 Ingestion

Import icustays.csv.gz as a tibble icustays_tble.

icustays_tble <- read_csv("~/mimic/icu/icustays.csv.gz") |>
  print()

Rows: 73181 Columns: 8
── Column specification ────────────────────────────────────────────────────────
Delimiter: ","
chr  (2): first_careunit, last_careunit
dbl  (4): subject_id, hadm_id, stay_id, los
dttm (2): intime, outtime

ℹ Use `spec()` to retrieve the full column specification for this data.
ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

# A tibble: 73,181 × 8
   subject_id  hadm_id  stay_id first_careunit last_careunit intime             
        <dbl>    <dbl>    <dbl> <chr>          <chr>         <dttm>             
 1   10000032 29079034 39553978 Medical Inten… Medical Inte… 2180-07-23 14:00:00
 2   10000980 26913865 39765666 Medical Inten… Medical Inte… 2189-06-27 08:42:00
 3   10001217 24597018 37067082 Surgical Inte… Surgical Int… 2157-11-20 19:18:02
 4   10001217 27703517 34592300 Surgical Inte… Surgical Int… 2157-12-19 15:42:24
 5   10001725 25563031 31205490 Medical/Surgi… Medical/Surg… 2110-04-11 15:52:22
 6   10001884 26184834 37510196 Medical Inten… Medical Inte… 2131-01-11 04:20:05
 7   10002013 23581541 39060235 Cardiac Vascu… Cardiac Vasc… 2160-05-18 10:00:53
 8   10002155 20345487 32358465 Medical Inten… Medical Inte… 2131-03-09 21:33:00
 9   10002155 23822395 33685454 Coronary Care… Coronary Car… 2129-08-04 12:45:00
10   10002155 28994087 31090461 Medical/Surgi… Medical/Surg… 2130-09-24 00:50:00
# ℹ 73,171 more rows
# ℹ 2 more variables: outtime <dttm>, los <dbl>

Q2.2 Summary and visualization

How many unique subject_id? Can a subject_id have multiple ICU stays? Summarize the number of ICU stays per subject_id by graphs.

icustays_tble |>
  distinct(subject_id) |>
  summarize(rows = n())

# A tibble: 1 × 1
   rows
  <int>
1 50920

There are 50,920 unique subject_id.

icustays_tble |>
  summarize(rows = n())

# A tibble: 1 × 1
   rows
  <int>
1 73181

Without specifying unique values for subject_id, there are 73,181 total rows, which is more than the 50,920 rows from specifying unique values for subject_id. Thus, a subject_id can have multiple ICU stays.

icustays_tble |>
  group_by(subject_id) |>
  summarize(
    count = n()
  ) 

# A tibble: 50,920 × 2
   subject_id count
        <dbl> <int>
 1   10000032     1
 2   10000980     1
 3   10001217     2
 4   10001725     1
 5   10001884     1
 6   10002013     1
 7   10002155     3
 8   10002348     1
 9   10002428     4
10   10002430     1
# ℹ 50,910 more rows

ggplot(data = icustays_tble) +
  geom_bar(mapping = aes(x = subject_id)) + 
  labs(
    title = "Distribution of ICU stays by patient", 
    x = "Patient's Subject ID",
    y = "Count"
  ) 

#ERROR: graph not showing bars... too many subject ids?

Q3. admissions data

Information of the patients admitted into hospital is available in admissions.csv.gz. See https://mimic.mit.edu/docs/iv/modules/hosp/admissions/ for details of each field in this file. The first 10 lines are

zcat < ~/mimic/hosp/admissions.csv.gz | head

subject_id,hadm_id,admittime,dischtime,deathtime,admission_type,admit_provider_id,admission_location,discharge_location,insurance,language,marital_status,race,edregtime,edouttime,hospital_expire_flag
10000032,22595853,2180-05-06 22:23:00,2180-05-07 17:15:00,,URGENT,P874LG,TRANSFER FROM HOSPITAL,HOME,Other,ENGLISH,WIDOWED,WHITE,2180-05-06 19:17:00,2180-05-06 23:30:00,0
10000032,22841357,2180-06-26 18:27:00,2180-06-27 18:49:00,,EW EMER.,P09Q6Y,EMERGENCY ROOM,HOME,Medicaid,ENGLISH,WIDOWED,WHITE,2180-06-26 15:54:00,2180-06-26 21:31:00,0
10000032,25742920,2180-08-05 23:44:00,2180-08-07 17:50:00,,EW EMER.,P60CC5,EMERGENCY ROOM,HOSPICE,Medicaid,ENGLISH,WIDOWED,WHITE,2180-08-05 20:58:00,2180-08-06 01:44:00,0
10000032,29079034,2180-07-23 12:35:00,2180-07-25 17:55:00,,EW EMER.,P30KEH,EMERGENCY ROOM,HOME,Medicaid,ENGLISH,WIDOWED,WHITE,2180-07-23 05:54:00,2180-07-23 14:00:00,0
10000068,25022803,2160-03-03 23:16:00,2160-03-04 06:26:00,,EU OBSERVATION,P51VDL,EMERGENCY ROOM,,Other,ENGLISH,SINGLE,WHITE,2160-03-03 21:55:00,2160-03-04 06:26:00,0
10000084,23052089,2160-11-21 01:56:00,2160-11-25 14:52:00,,EW EMER.,P6957U,WALK-IN/SELF REFERRAL,HOME HEALTH CARE,Medicare,ENGLISH,MARRIED,WHITE,2160-11-20 20:36:00,2160-11-21 03:20:00,0
10000084,29888819,2160-12-28 05:11:00,2160-12-28 16:07:00,,EU OBSERVATION,P63AD6,PHYSICIAN REFERRAL,,Medicare,ENGLISH,MARRIED,WHITE,2160-12-27 18:32:00,2160-12-28 16:07:00,0
10000108,27250926,2163-09-27 23:17:00,2163-09-28 09:04:00,,EU OBSERVATION,P38XXV,EMERGENCY ROOM,,Other,ENGLISH,SINGLE,WHITE,2163-09-27 16:18:00,2163-09-28 09:04:00,0
10000117,22927623,2181-11-15 02:05:00,2181-11-15 14:52:00,,EU OBSERVATION,P2358X,EMERGENCY ROOM,,Other,ENGLISH,DIVORCED,WHITE,2181-11-14 21:51:00,2181-11-15 09:57:00,0

Q3.1 Ingestion

Import admissions.csv.gz as a tibble admissions_tble.

Answer:

admissions_tble <- read_csv("~/mimic/hosp/admissions.csv.gz") |>
  print()

Rows: 431231 Columns: 16
── Column specification ────────────────────────────────────────────────────────
Delimiter: ","
chr  (8): admission_type, admit_provider_id, admission_location, discharge_l...
dbl  (3): subject_id, hadm_id, hospital_expire_flag
dttm (5): admittime, dischtime, deathtime, edregtime, edouttime

ℹ Use `spec()` to retrieve the full column specification for this data.
ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

# A tibble: 431,231 × 16
   subject_id  hadm_id admittime           dischtime          
        <dbl>    <dbl> <dttm>              <dttm>             
 1   10000032 22595853 2180-05-06 22:23:00 2180-05-07 17:15:00
 2   10000032 22841357 2180-06-26 18:27:00 2180-06-27 18:49:00
 3   10000032 25742920 2180-08-05 23:44:00 2180-08-07 17:50:00
 4   10000032 29079034 2180-07-23 12:35:00 2180-07-25 17:55:00
 5   10000068 25022803 2160-03-03 23:16:00 2160-03-04 06:26:00
 6   10000084 23052089 2160-11-21 01:56:00 2160-11-25 14:52:00
 7   10000084 29888819 2160-12-28 05:11:00 2160-12-28 16:07:00
 8   10000108 27250926 2163-09-27 23:17:00 2163-09-28 09:04:00
 9   10000117 22927623 2181-11-15 02:05:00 2181-11-15 14:52:00
10   10000117 27988844 2183-09-18 18:10:00 2183-09-21 16:30:00
# ℹ 431,221 more rows
# ℹ 12 more variables: deathtime <dttm>, admission_type <chr>,
#   admit_provider_id <chr>, admission_location <chr>,
#   discharge_location <chr>, insurance <chr>, language <chr>,
#   marital_status <chr>, race <chr>, edregtime <dttm>, edouttime <dttm>,
#   hospital_expire_flag <dbl>

Q3.2 Summary and visualization

Summarize the following information by graphics and explain any patterns you see.

• number of admissions per patient

Answer:

ggplot(data = admissions_tble) +
  geom_bar(mapping = aes(x = subject_id)) + 
  labs(
    title = "Distribution of admissions by patient", 
    x = "Patient's Subject ID",
    y = "Count"
  ) 

#ERROR: graph not showing bars... too many subject ids?

• admission hour (anything unusual?)

Answer:

ggplot(data = admissions_tble) +
  geom_bar(mapping = aes(x = hour(admittime))) + 
  labs(
    title = "Distribution of the hour of admission", 
    x = "Hour of Admission",
    y = "Count"
  ) 

Yes, there is an unusually high number of admissions that occur at 0am and 7am, relative to the other hours in the morning. Aside from these two unusual hours, admissions are generally low in the morning; however, admissions start to increase in the early afternoon and stay at high numbers during the night.

• admission minute (anything unusual?)

Answer:

ggplot(data = admissions_tble) +
  geom_bar(mapping = aes(x = minute(admittime))) + 
  labs(
    title = "Distribution of the minute of admission", 
    x = "Minute of Admission",
    y = "Count"
  ) 

Yes, there is an unusually high number of admissions that occur at the 0 minute, 15 minute, 30 minute, and 45 minute. This could be due a tendency of healthcare workers to round to the nearest quarter of the hour when recording the admission time. Aside from these unusual minutes, all other minutes have similar numbers of admissions.

• length of hospital stay (from admission to discharge) (anything unusual?)

Answer:

ggplot(data = admissions_tble) +
  geom_bar(mapping = aes(x = (as.duration(admittime %--% dischtime)/86400))) + 
  labs(
    title = "Distribution of hospital stay length", 
    x = "Hospital Stay Length (Days)",
    y = "Count"
  ) 

Most hospital stays are relatively short, spanning a day to a few days. However, there do seem to be some hospital stays that are longer, spanning several days to weeks. The x axis of the graph extends to 300 days, indicating that there is an unusually long hospital stay that lasted around 300 days.

According to the MIMIC-IV documentation,

All dates in the database have been shifted to protect patient confidentiality. Dates will be internally consistent for the same patient, but randomly distributed in the future. Dates of birth which occur in the present time are not true dates of birth. Furthermore, dates of birth which occur before the year 1900 occur if the patient is older than 89. In these cases, the patient’s age at their first admission has been fixed to 300.

Q4. patients data

Patient information is available in patients.csv.gz. See https://mimic.mit.edu/docs/iv/modules/hosp/patients/ for details of each field in this file. The first 10 lines are

zcat < ~/mimic/hosp/patients.csv.gz | head

subject_id,gender,anchor_age,anchor_year,anchor_year_group,dod
10000032,F,52,2180,2014 - 2016,2180-09-09
10000048,F,23,2126,2008 - 2010,
10000068,F,19,2160,2008 - 2010,
10000084,M,72,2160,2017 - 2019,2161-02-13
10000102,F,27,2136,2008 - 2010,
10000108,M,25,2163,2014 - 2016,
10000115,M,24,2154,2017 - 2019,
10000117,F,48,2174,2008 - 2010,
10000178,F,59,2157,2017 - 2019,

Q4.1 Ingestion

Import patients.csv.gz (https://mimic.mit.edu/docs/iv/modules/hosp/patients/) as a tibble patients_tble.

Answer:

patients_tble <- read_csv("~/mimic/hosp/patients.csv.gz") |>
  print()

Rows: 299712 Columns: 6
── Column specification ────────────────────────────────────────────────────────
Delimiter: ","
chr  (2): gender, anchor_year_group
dbl  (3): subject_id, anchor_age, anchor_year
date (1): dod

ℹ Use `spec()` to retrieve the full column specification for this data.
ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

# A tibble: 299,712 × 6
   subject_id gender anchor_age anchor_year anchor_year_group dod       
        <dbl> <chr>       <dbl>       <dbl> <chr>             <date>    
 1   10000032 F              52        2180 2014 - 2016       2180-09-09
 2   10000048 F              23        2126 2008 - 2010       NA        
 3   10000068 F              19        2160 2008 - 2010       NA        
 4   10000084 M              72        2160 2017 - 2019       2161-02-13
 5   10000102 F              27        2136 2008 - 2010       NA        
 6   10000108 M              25        2163 2014 - 2016       NA        
 7   10000115 M              24        2154 2017 - 2019       NA        
 8   10000117 F              48        2174 2008 - 2010       NA        
 9   10000178 F              59        2157 2017 - 2019       NA        
10   10000248 M              34        2192 2014 - 2016       NA        
# ℹ 299,702 more rows

Q4.2 Summary and visualization

Summarize variables gender and anchor_age by graphics, and explain any patterns you see.

Answer:

ggplot(data = patients_tble) +
  geom_violin(mapping = aes(x = gender, y = anchor_age)) + 
  labs(
    title = "Distribution of patient age by patient gender", 
    x = "Gender",
    y = "Age"
  ) 

ggplot(data = patients_tble) +
  geom_histogram(binwidth = 2, mapping = aes(x = anchor_age, fill = gender),
                 position = "dodge") + 
  labs(
    title = "Distribution of patient age by patient gender",
    x = "Age",
    y = "Count",
    fill = "Gender"
  ) 

In general, there is a larger share of young adult patients compared to adult and elderly patients, for both genders. This observation is surprising, as we would assume the opposite with more elderly patients and less young adult patients. However, the oldest elderly patients seem to make up a sizable share of the total patients, likely due to worsening health conditions. Across young adult and elderly patients, there is a larger share of female patients, while across adult patients, there is a larger share of male patients. This could be due to multiple factors or a combination of factors, e.g. women may be more likely to seek out medical care or come in more often for female-specific health conditions that are critical at younger and older ages.

Q5. Lab results

labevents.csv.gz (https://mimic.mit.edu/docs/iv/modules/hosp/labevents/) contains all laboratory measurements for patients. The first 10 lines are

zcat < ~/mimic/hosp/labevents.csv.gz | head

labevent_id,subject_id,hadm_id,specimen_id,itemid,order_provider_id,charttime,storetime,value,valuenum,valueuom,ref_range_lower,ref_range_upper,flag,priority,comments
1,10000032,,45421181,51237,P28Z0X,2180-03-23 11:51:00,2180-03-23 15:15:00,1.4,1.4,,0.9,1.1,abnormal,ROUTINE,
2,10000032,,45421181,51274,P28Z0X,2180-03-23 11:51:00,2180-03-23 15:15:00,___,15.1,sec,9.4,12.5,abnormal,ROUTINE,VERIFIED.
3,10000032,,52958335,50853,P28Z0X,2180-03-23 11:51:00,2180-03-25 11:06:00,___,15,ng/mL,30,60,abnormal,ROUTINE,NEW ASSAY IN USE ___: DETECTS D2 AND D3 25-OH ACCURATELY.
4,10000032,,52958335,50861,P28Z0X,2180-03-23 11:51:00,2180-03-23 16:40:00,102,102,IU/L,0,40,abnormal,ROUTINE,
5,10000032,,52958335,50862,P28Z0X,2180-03-23 11:51:00,2180-03-23 16:40:00,3.3,3.3,g/dL,3.5,5.2,abnormal,ROUTINE,
6,10000032,,52958335,50863,P28Z0X,2180-03-23 11:51:00,2180-03-23 16:40:00,109,109,IU/L,35,105,abnormal,ROUTINE,
7,10000032,,52958335,50864,P28Z0X,2180-03-23 11:51:00,2180-03-23 16:40:00,___,8,ng/mL,0,8.7,,ROUTINE,MEASURED BY ___.
8,10000032,,52958335,50868,P28Z0X,2180-03-23 11:51:00,2180-03-23 16:40:00,12,12,mEq/L,8,20,,ROUTINE,
9,10000032,,52958335,50878,P28Z0X,2180-03-23 11:51:00,2180-03-23 16:40:00,143,143,IU/L,0,40,abnormal,ROUTINE,

d_labitems.csv.gz (https://mimic.mit.edu/docs/iv/modules/hosp/d_labitems/) is the dictionary of lab measurements.

zcat < ~/mimic/hosp/d_labitems.csv.gz | head

itemid,label,fluid,category
50801,Alveolar-arterial Gradient,Blood,Blood Gas
50802,Base Excess,Blood,Blood Gas
50803,"Calculated Bicarbonate, Whole Blood",Blood,Blood Gas
50804,Calculated Total CO2,Blood,Blood Gas
50805,Carboxyhemoglobin,Blood,Blood Gas
50806,"Chloride, Whole Blood",Blood,Blood Gas
50808,Free Calcium,Blood,Blood Gas
50809,Glucose,Blood,Blood Gas
50810,"Hematocrit, Calculated",Blood,Blood Gas

We are interested in the lab measurements of creatinine (50912), potassium (50971), sodium (50983), chloride (50902), bicarbonate (50882), hematocrit (51221), white blood cell count (51301), and glucose (50931). Retrieve a subset of labevents.csv.gz that only containing these items for the patients in icustays_tble. Further restrict to the last available measurement (by storetime) before the ICU stay. The final labevents_tble should have one row per ICU stay and columns for each lab measurement.

Hint: Use the Parquet format you generated in Homework 2. For reproducibility, make labevents_pq folder available at the current working directory hw3, for example, by a symbolic link.

Answer:

labevents_subset <- arrow::open_dataset("labevents_pq/part-0.parquet", 
                                      format = "parquet") |>
  select(subject_id, itemid, storetime, valuenum) |>
  filter(itemid == 50912 | itemid == 50971 | itemid == 50983 | itemid == 50902 |
           itemid == 50882 | itemid == 51221 | itemid == 51301 | 
           itemid == 50931) |>
  as_tibble()
icustays_subset <- icustays_tble |> 
  select(subject_id, stay_id, intime)
labevents_tble <- left_join(icustays_subset, labevents_subset, 
                            by = "subject_id", 
                            relationship = "many-to-many") |>
  mutate(span = as.duration(storetime - intime)) |> 
  group_by(subject_id, stay_id, itemid) |>
  arrange(span, .by_group = TRUE) |>
  filter(span < 0) |>
  slice_tail() |>
  select(-c(intime, storetime, span)) |>
  pivot_wider(names_from = itemid, values_from = valuenum) |>
  rename(
    creatinine = "50912",
    potassium = "50971",
    sodium = "50983",
    chloride = "50902",
    bicarbonate = "50882",
    hematocrit = "51221",
    wbc = "51301",
    glucose = "50931"
  ) |>
  ungroup() |>
  print()

# A tibble: 68,467 × 10
   subject_id  stay_id bicarbonate chloride creatinine glucose potassium sodium
        <dbl>    <dbl>       <dbl>    <dbl>      <dbl>   <dbl>     <dbl>  <dbl>
 1   10000032 39553978          25       95        0.7     102       6.7    126
 2   10000980 39765666          21      109        2.3      89       3.9    144
 3   10001217 34592300          30      104        0.5      87       4.1    142
 4   10001217 37067082          22      108        0.6     112       4.2    142
 5   10001725 31205490          NA       98       NA        NA       4.1    139
 6   10001884 37510196          30       88        1.1     141       4.5    130
 7   10002013 39060235          24      102        0.9     288       3.5    137
 8   10002155 31090461          23       98        2.8     117       4.9    135
 9   10002155 32358465          26       85        1.4     133       5.7    120
10   10002155 33685454          24      105        1.1     138       4.6    139
# ℹ 68,457 more rows
# ℹ 2 more variables: hematocrit <dbl>, wbc <dbl>

Q6. Vitals from charted events

chartevents.csv.gz (https://mimic.mit.edu/docs/iv/modules/icu/chartevents/) contains all the charted data available for a patient. During their ICU stay, the primary repository of a patient’s information is their electronic chart. The itemid variable indicates a single measurement type in the database. The value variable is the value measured for itemid. The first 10 lines of chartevents.csv.gz are

zcat < ~/mimic/icu/chartevents.csv.gz | head

subject_id,hadm_id,stay_id,caregiver_id,charttime,storetime,itemid,value,valuenum,valueuom,warning
10000032,29079034,39553978,47007,2180-07-23 21:01:00,2180-07-23 22:15:00,220179,82,82,mmHg,0
10000032,29079034,39553978,47007,2180-07-23 21:01:00,2180-07-23 22:15:00,220180,59,59,mmHg,0
10000032,29079034,39553978,47007,2180-07-23 21:01:00,2180-07-23 22:15:00,220181,63,63,mmHg,0
10000032,29079034,39553978,47007,2180-07-23 22:00:00,2180-07-23 22:15:00,220045,94,94,bpm,0
10000032,29079034,39553978,47007,2180-07-23 22:00:00,2180-07-23 22:15:00,220179,85,85,mmHg,0
10000032,29079034,39553978,47007,2180-07-23 22:00:00,2180-07-23 22:15:00,220180,55,55,mmHg,0
10000032,29079034,39553978,47007,2180-07-23 22:00:00,2180-07-23 22:15:00,220181,62,62,mmHg,0
10000032,29079034,39553978,47007,2180-07-23 22:00:00,2180-07-23 22:15:00,220210,20,20,insp/min,0
10000032,29079034,39553978,47007,2180-07-23 22:00:00,2180-07-23 22:15:00,220277,95,95,%,0

d_items.csv.gz (https://mimic.mit.edu/docs/iv/modules/icu/d_items/) is the dictionary for the itemid in chartevents.csv.gz.

zcat < ~/mimic/icu/d_items.csv.gz | head

itemid,label,abbreviation,linksto,category,unitname,param_type,lownormalvalue,highnormalvalue
220001,Problem List,Problem List,chartevents,General,,Text,,
220003,ICU Admission date,ICU Admission date,datetimeevents,ADT,,Date and time,,
220045,Heart Rate,HR,chartevents,Routine Vital Signs,bpm,Numeric,,
220046,Heart rate Alarm - High,HR Alarm - High,chartevents,Alarms,bpm,Numeric,,
220047,Heart Rate Alarm - Low,HR Alarm - Low,chartevents,Alarms,bpm,Numeric,,
220048,Heart Rhythm,Heart Rhythm,chartevents,Routine Vital Signs,,Text,,
220050,Arterial Blood Pressure systolic,ABPs,chartevents,Routine Vital Signs,mmHg,Numeric,90,140
220051,Arterial Blood Pressure diastolic,ABPd,chartevents,Routine Vital Signs,mmHg,Numeric,60,90
220052,Arterial Blood Pressure mean,ABPm,chartevents,Routine Vital Signs,mmHg,Numeric,,

We are interested in the vitals for ICU patients: heart rate (220045), systolic non-invasive blood pressure (220179), diastolic non-invasive blood pressure (220180), body temperature in Fahrenheit (223761), and respiratory rate (220210). Retrieve a subset of chartevents.csv.gz only containing these items for the patients in icustays_tble. Further restrict to the first vital measurement within the ICU stay. The final chartevents_tble should have one row per ICU stay and columns for each vital measurement.

Hint: Use the Parquet format you generated in Homework 2. For reproducibility, make chartevents_pq folder available at the current working directory, for example, by a symbolic link.

Answer:

chartevents_subset <- arrow::open_dataset("chartevents_pq/part-0.parquet", 
                                      format = "parquet") |>
  select(subject_id, stay_id, charttime, itemid, valuenum) |>
  filter(itemid == 220045 | itemid == 220179 | itemid == 220180 | 
           itemid == 223761 | itemid == 220210) |>
  as_tibble()
icustays_subset <- icustays_tble |> 
  select(subject_id, stay_id, intime)
chartevents_tble <- left_join(chartevents_subset, icustays_subset, 
                                  by = c("subject_id", "stay_id"), 
                                  relationship = "many-to-many") |> 
  mutate(span = as.duration(charttime - intime)) |>
  group_by(subject_id, stay_id, itemid) |>
  arrange(span, .by_group = TRUE) |>
  slice_head() |> 
  select(-c(intime, charttime, span)) |>
  pivot_wider(names_from = itemid, values_from = valuenum) |>
  rename(
    heart_rate = "220045",
    non_invasive_blood_pressure_systolic = "220179",
    non_invasive_blood_pressure_diastolic = "220180",
    temperature_fahrenheit = "223761",
    respiratory_rate = "220210"
  ) |> 
  ungroup() |>
  print()

# A tibble: 73,164 × 7
   subject_id  stay_id heart_rate non_invasive_blood_pr…¹ non_invasive_blood_p…²
        <dbl>    <dbl>      <dbl>                   <dbl>                  <dbl>
 1   10000032 39553978         91                      84                     48
 2   10000980 39765666         77                     150                     77
 3   10001217 34592300         96                     167                     95
 4   10001217 37067082         86                     151                     90
 5   10001725 31205490         55                      73                     56
 6   10001884 37510196         38                     180                     12
 7   10002013 39060235         80                     104                     70
 8   10002155 31090461         94                     118                     51
 9   10002155 32358465         98                     109                     65
10   10002155 33685454         68                     126                     61
# ℹ 73,154 more rows
# ℹ abbreviated names: ¹​non_invasive_blood_pressure_systolic,
#   ²​non_invasive_blood_pressure_diastolic
# ℹ 2 more variables: respiratory_rate <dbl>, temperature_fahrenheit <dbl>

#row 6, respiratory rate has diff value from photo

Q7. Putting things together

Let us create a tibble mimic_icu_cohort for all ICU stays, where rows are all ICU stays of adults (age at intime >= 18) and columns contain at least following variables

• all variables in icustays_tble
  
• all variables in admissions_tble
  
• all variables in patients_tble
• the last lab measurements before the ICU stay in labevents_tble
• the first vital measurements during the ICU stay in chartevents_tble

The final mimic_icu_cohort should have one row per ICU stay and columns for each variable.

Answer:

mimic_icu_cohort <- left_join(icustays_tble, admissions_tble, 
                              by = c("subject_id", "hadm_id")) |>
  left_join(patients_tble, by = "subject_id") |>
  left_join(labevents_tble, by = c("subject_id", "stay_id")) |>
  left_join(chartevents_tble, by = c("subject_id", "stay_id")) |>
  mutate(intime_year = year(intime),
         year_diff = intime_year - anchor_year,
         intime_age = anchor_age + year_diff) |>
  filter(intime_age >= 18) |>
  select(-c(intime_year, year_diff)) |>
  print()

# A tibble: 73,181 × 41
   subject_id  hadm_id  stay_id first_careunit last_careunit intime             
        <dbl>    <dbl>    <dbl> <chr>          <chr>         <dttm>             
 1   10000032 29079034 39553978 Medical Inten… Medical Inte… 2180-07-23 14:00:00
 2   10000980 26913865 39765666 Medical Inten… Medical Inte… 2189-06-27 08:42:00
 3   10001217 24597018 37067082 Surgical Inte… Surgical Int… 2157-11-20 19:18:02
 4   10001217 27703517 34592300 Surgical Inte… Surgical Int… 2157-12-19 15:42:24
 5   10001725 25563031 31205490 Medical/Surgi… Medical/Surg… 2110-04-11 15:52:22
 6   10001884 26184834 37510196 Medical Inten… Medical Inte… 2131-01-11 04:20:05
 7   10002013 23581541 39060235 Cardiac Vascu… Cardiac Vasc… 2160-05-18 10:00:53
 8   10002155 20345487 32358465 Medical Inten… Medical Inte… 2131-03-09 21:33:00
 9   10002155 23822395 33685454 Coronary Care… Coronary Car… 2129-08-04 12:45:00
10   10002155 28994087 31090461 Medical/Surgi… Medical/Surg… 2130-09-24 00:50:00
# ℹ 73,171 more rows
# ℹ 35 more variables: outtime <dttm>, los <dbl>, admittime <dttm>,
#   dischtime <dttm>, deathtime <dttm>, admission_type <chr>,
#   admit_provider_id <chr>, admission_location <chr>,
#   discharge_location <chr>, insurance <chr>, language <chr>,
#   marital_status <chr>, race <chr>, edregtime <dttm>, edouttime <dttm>,
#   hospital_expire_flag <dbl>, gender <chr>, anchor_age <dbl>, …

Above is my final mimic_icu_cohort. The number of rows in my cohort (73,181) does not exactly match the number of rows in the picture (73,097), which is because I filtered the age at intime by >= 18 as the instructions requested. However, when I tested out filtering the age at intime by > 18, the number of rows was 73,097, which matched the picture. I kept the filter as age at intime >= 18 to comply with the instructions.

Q8. Exploratory data analysis (EDA)

Summarize the following information about the ICU stay cohort mimic_icu_cohort using appropriate numerics or graphs:

• Length of ICU stay los vs demographic variables (race, insurance, marital_status, gender, age at intime)

Answer:

Race

ggplot(data = mimic_icu_cohort) +
  geom_col(mapping = aes(x = race, y = los)) + 
  labs(
    title = "Distribution of ICU stay length by patient race", 
    x = "Race",
    y = "Total ICU Stay Length (Fractional Days)"
  ) + 
  coord_flip() 

White patients have the longest total ICU stay, followed by patients with an unknown race and Black/African American patients.

Insurance

ggplot(data = mimic_icu_cohort) +
  geom_col(mapping = aes(x = insurance, y = los)) + 
  labs(
    title = "Distribution of ICU stay length by patient's insurance", 
    x = "Insurance",
    y = "Total ICU Stay Length (Fractional Days)"
  ) +
  coord_flip()

Patients with insurance other than Medicare and Medicaid have the longest total ICU stay, closely followed by patients with Medicare insurance. Compared to patients with Medicare or other insurance, patients with Medicaid have a shorter total ICU stay.

Marital Status

ggplot(data = mimic_icu_cohort) +
  geom_col(mapping = aes(x = marital_status, y = los)) + 
  labs(
    title = "Distribution of ICU stay length by patient's marital status", 
    x = "Marital Status",
    y = "Total ICU Stay Length (Fractional Days)"
  ) + 
  coord_flip()

Married patients have the longest total ICU stay, followed by single patients. Compared to married or single patients, widowed and divorced patients as well as patients with missing marital status data have shorter total ICU stays.

Gender

ggplot(data = mimic_icu_cohort) +
  geom_col(mapping = aes(x = gender, y = los)) + 
  labs(
    title = "Distribution of ICU stay length by patient gender", 
    x = "Gender",
    y = "Total ICU Stay Length (Fractional Days)"
  ) + 
  coord_flip()

Male patients have a longer total ICU stay, compared to female patients.

Age

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = intime_age, y = los), 
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by patient age", 
    caption = "Patient age at time of transfer to ICU.",
    x = "Age",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Across all ages, most ICU stays tend to be 30 days or less, though there are some patients with ICU stays longer than 30 days. Generally, the youngest and oldest patients tend to have shorter ICU stays, while a larger share of adults aged 50-90 years tend to have longer ICU stays.

• Length of ICU stay los vs the last available lab measurements before ICU stay

Answer:

Bicarbonate

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = bicarbonate, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by bicarbonate measurement",
    x = "Bicarbonate (mEq/L)",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 9050 rows containing missing values (`geom_point()`).

Patients with bicarbonate levels between ~20-30 mEq/L measured right before their ICU stay tend to have longer ICU stays, while patients with very low or very high bicarbonate levels tend to have shorter ICU stays.

Chloride

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = chloride, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by chloride measurement",
    x = "Chloride (mEq/L)",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 8883 rows containing missing values (`geom_point()`).

Patients with chloride levels ~100 mEq/L tend to have the longest ICU stays, while patients with very low or very high chloride levels tend to have shorter ICU stays.

Creatinine

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = creatinine, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by creatinine measurement",
    x = "Creatinine (mg/dL)",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 5770 rows containing missing values (`geom_point()`).

Patients with very low creatinine levels tend to have longer ICU stays, while patients with higher creatinine levels tend to have shorter ICU stays.

Glucose

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = glucose, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by glucose measurement",
    x = "Glucose (mg/dL)",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 9099 rows containing missing values (`geom_point()`).

Patients with low glucose levels tend to have longer ICU stays, while patients with higher glucose levels tend to have shorter ICU stays.

Potassium

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = potassium, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by potassium measurement",
    x = "Potassium (mEq/L)",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 8901 rows containing missing values (`geom_point()`).

Patients with potassium levels between ~3-6 mEq/L tend to have longer ICU stays, while patients with very low or very high potassium levels tend to have shorter ICU stays.

Sodium

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = sodium, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by sodium measurement",
    x = "Sodium (mEq/L)",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 8872 rows containing missing values (`geom_point()`).

Patients with sodium levels between ~125-150 mEq/L tend to have longer ICU stays, while patients with lower and higher sodium levels tend to have shorter ICU stays.

Hematocrit

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = hematocrit, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by hematocrit measurement",
    x = "Hematocrit (%)",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 5017 rows containing missing values (`geom_point()`).

Patients with hematocrit levels between ~25-45% tend to longer ICU stays, while patients with lower and higher hematocrit levels tend to have shorter ICU stays.

White Blood Cell

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = wbc, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by white blood cell count",
    x = "White Blood Cell Count",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 5094 rows containing missing values (`geom_point()`).

Patients with very low white blood cell counts tend to have longer ICU stays, while patients with higher white blood cell counts tend to have shorter ICU stays.

• Length of ICU stay los vs the average vital measurements within the first hour of ICU stay

Answer:

Heart Rate

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = heart_rate, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by heart rate measurement",
    x = "Heart Rate (bpm)",
    y = "ICU Stay Length (Fractional Days)"
  )

Warning: Removed 18 rows containing missing values (`geom_point()`).

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = heart_rate, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by heart rate measurement",
    x = "Heart Rate (bpm)",
    y = "ICU Stay Length (Fractional Days)"
  ) + 
  coord_cartesian(xlim = c(0, 250))

Warning: Removed 18 rows containing missing values (`geom_point()`).

The first plot shows one observation with an extremely high heart rate (possibly due to a recording error?), which masks the variability in the distribution. The second plot ignores this observation, zooming into the distribution of heart rates between 0-250 bpm. In the second plot, we can see that patients with heart rates between ~75-125 bpm tend to have longer ICU stays, compared to patients with lower or higher heart rates.

Systolic Non-invasive Blood Pressure

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = non_invasive_blood_pressure_systolic, y = los)) +
  labs(
    title = "Distribution of ICU stay length by systolic non-invasive blood pressure measurement",
    x = "Systolic Non-invasive Blood Pressure (mmHg)",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 950 rows containing missing values (`geom_point()`).

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = non_invasive_blood_pressure_systolic, y = los)) +
  labs(
    title = "Distribution of ICU stay length by systolic non-invasive blood pressure measurement",
    x = "Systolic Non-invasive Blood Pressure (mmHg)",
    y = "ICU Stay Length (Fractional Days)"
  ) + 
  coord_cartesian(xlim = c(0, 275))

Warning: Removed 950 rows containing missing values (`geom_point()`).

The first plot shows two observation with extremely high systolic non-invasive blood pressures (possibly due to recording errors?), which masks the variability in the distribution. The second plot ignores these observations, zooming into the distribution of systolic non-invasive blood pressures between 0-275 mmHg. In the second plot, we can see that patients with systolic non-invasive blood pressures between ~100-150 mmHg tend to have longer ICU stays, compared to patients with lower or higher blood pressures.

Diastolic Non-invasive Blood Pressure

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = non_invasive_blood_pressure_diastolic, 
                           y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by diastolic non-invasive blood pressure measurement",
    x = "Diastolic Non-invasive Blood Pressure (mmHg)",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 953 rows containing missing values (`geom_point()`).

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = non_invasive_blood_pressure_diastolic, 
                           y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by diastolic non-invasive blood pressure measurement",
    x = "Diastolic Non-invasive Blood Pressure (mmHg)",
    y = "ICU Stay Length (Fractional Days)"
  ) + 
  coord_cartesian(xlim = c(0, 225))

Warning: Removed 953 rows containing missing values (`geom_point()`).

The first plot shows several observations with extremely high diastolic non-invasive blood pressures (possibly due to recording errors?), which masks the variability in the distribution. The second plot ignores these observation, zooming into the distribution of diastolic non-invasive blood pressures between 0-225 mmHg. In the second plot, we can see that patients with diastolic non-invasive blood pressures between ~50-100 mmHg tend to have longer ICU stays, compared to patients with lower or higher blood pressures.

Respiratory Rate

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = respiratory_rate, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by respiratory rate measurement",
    x = "Respiratory Rate (insp/min)",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 91 rows containing missing values (`geom_point()`).

Patients with respiratory rates ~25 insp/min tend to have longer ICU stays, while patients with lower or higher respiratory rates tend to have shorter ICU stays.

Body Temperature

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = temperature_fahrenheit, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by body temperature measurement",
    x = "Body Temperature (degrees Fahrenheit)",
    y = "ICU Stay Length (Fractional Days)"
  ) 

Warning: Removed 1249 rows containing missing values (`geom_point()`).

ggplot(data = mimic_icu_cohort) +
  geom_point(mapping = aes(x = temperature_fahrenheit, y = los),
             position = "jitter") +
  labs(
    title = "Distribution of ICU stay length by body temperature measurement",
    x = "Body Temperature (degrees Fahrenheit)",
    y = "ICU Stay Length (Fractional Days)"
  ) + 
  coord_cartesian(xlim = c(0, 105))

Warning: Removed 1249 rows containing missing values (`geom_point()`).

The first plot shows two observations with extremely high body temperatures (possibly due to recording errors?), which masks the variability in the distribution. The second plot ignores these observation, zooming into the distribution of diastolic non-invasive blood pressures between 0-105 degrees Fahrenheit. In the second plot, we can see that most observations are clustered around the average human body temperature, with the longest ICU stays observed for patients with body temperatures slightly below 100 degrees Fahrenheit. Unusually, there are observations with extremely low body temperatures as well.

• Length of ICU stay los vs first ICU unit

Answer:

ggplot(data = mimic_icu_cohort) +
  geom_col(mapping = aes(x = first_careunit, y = los)) + 
  labs(
    title = "Distribution of ICU stay length by first ICU unit", 
    x = "First ICU Unit",
    y = "Total ICU Stay Length (Fractional Days)"
  ) + 
  coord_flip()

Patients transferred to the Medical Intensive Care Unit (MICU) have the longest total ICU stay, followed by patients transferred to the Surgical Intensive Care Unit (SICU) and the Medical/Surgical Intensive Care Unit (MICU/SICU). Patients transferred to Neuro Stepdown have the shortest total ICU stay.